The present invention relates to an image forming apparatus for forming an image wherein a photoreceptor is scanned to be exposed to light by a light beam, and to an assembling method of an exposure unit in the image forming apparatus.
In the image forming apparatus for forming an image wherein a photoreceptor is scanned to be exposed to light by a light beam, accuracy of incident position of the light beam on the photoreceptor has an influence on image quality. Therefore, an exposure unit is structured so that the light beam may enter at high accuracy.
In a color image forming apparatus for forming a color image by conducting a plurality of exposures, forming a plurality of images and thereby by superposing the plural images, in particular, it is requested to keep the position stated above accurately.
Typical one that conducts scanning exposure with a light beam is an exposure unit employing a laser, and with respect to adjustment of the position stated above in a laser exposure unit, there is disclosed in U.S. Pat. No. 2,570,176 official gazette, for example, an adjustment mechanism for adjusting a position and an angle of the exposure unit having a laser light source and a scanning exposure optical system in X, Y and Z directions. This adjustment mechanism adjusts at two points representing both ends of each side of the square exposure unit for each of X, Y and Z directions, and thereby adjusts the incident position of the light beam on the photoreceptor.
Each of many color image forming apparatuses is equipped with a plurality of exposure units which form a plurality of color images, and these exposure units are provided in the image forming apparatus at high positional accuracy. In particular, it is required that relative positional accuracy between the exposure units is high. If the positional accuracy between the exposure units is not satisfactory, displacement is caused between color images to cause doubling, resulting in deterioration of image quality. The positional relationship between exposure units needs to be maintained during the operation period of the image forming apparatus.
To satisfy the conditions about positions of the exposure units, a plurality of exposure units have been combined with UV adhesive agents, for example.
In the adjustment mechanism disclosed in the aforesaid patent publication, there are provided 6 adjustment means in total, because adjustment is made at two points for each of X, Y and Z directions. Therefore, the adjustment is complicated. Further, there has not been disclosed a concrete adjustment mechanism capable of attaining simple structure and high adjustment accuracy, in the prior art.
Further, in the fixing means to fix between exposure units by adhesive agents, a great many hours are needed for securing desired strength, which has been a problem in manufacture.
An object of the invention is to solve the aforesaid problems in conventional image forming apparatuses employing a light beam.